Yahoo is now owned by Verizon under the Oath inc. name. Tumblr seems fine and so is their mail service. Although a new e-mail system is soon to come out.
Don't know why they dumped Messenger but I never used it anyway, nor Yahoo Answers.
When a new company takes over? They usually try to trim some of the fat off the old system and add a couple of new things. You'll see more by the end of the year.